In climates that have freezing seasonal temperatures, the maintenance of swimming pools includes a winterizing process. As part of the winterizing process, the system of conduits and pipes that support water flow into and out of the pool are drained because water left in those pipes and conduits will freeze and expand as the temperature drops below freezing, damaging the pipes and fittings. For in-ground pools, the winterizing process typically involves the steps of draining water from all pipes situated above the frost line (typically to three feet below ground level), closing exposed orifices in the pool side wall to prevent ingress of water, debris, rain or snow into the pipes and conduits, and removing or protecting outside mechanical equipment. It is necessary to prepare swimming pools for such temperatures in order to avoid extensive damage, particularly to those pipes and conduits that are buried in the ground but above the frost line.
In most in-ground pool systems, the return and drain pipes are each fitted through its respective aperture in the pool wall. The pool apertures are typically situated well below the normal water line, perhaps by as much as thirty to fifty centimeters. In prior art winterization procedures, one must first reduce the water level to below the aperture levels so that the water remaining in the pipes above the frost line can be drained therefrom. Such a procedure requires extensive draining of pool water, which can take up to eight hours. Draining to that level can involve the removal of several thousand liters of water from a typical residential swimming pool, perhaps as much as twenty-five thousand liters. The drained water usually is wasted. After the pool is drained, the pipe ends are capped so that water and moisture cannot enter the pipes. The winterization process further includes refilling of the pool to about the normal water level to protect the pool structure from collapsing as the surrounding ground freezes and expands.
Referring to the drawings, a conventional swimming pool arrangement is illustrated by FIG. 1; the arrangement comprises generally the pool whose peripheral rectangular wall is shown at 11 and a circulation and filtration system, the several parts of which are encompassed within the area of the broken line 10, is situated contiguous to one end of the pool 11. Typically, the plumbing accessories include at least a main drain 12 which draws water and sediment from the bottom of the swimming pool and a skimmer 13 through which water to be filtered and re-circulated is withdrawn and debris is removed. In the circulation process, water withdrawn from the pool through the main drain and from the skimmer is filtered and optionally chemically treated and returned to the swimming pool through returns such as shown at 14 and 15.
A pump 24 withdraws water from the swimming pool, the water is filtered at 25, and through use of appropriate valves, such as 21 and 23, is reintroduced into the swimming pool at return points such as those illustrated at 14 and 15. Suction piping, some of which is illustrated at 19 and 20, and discharge piping, as shown at 16, 17 and 18, are utilized to move the water between the pump and the pool. The pool has a plurality of apertures to accommodate return piping 14 and 15 and main drain piping 20. Likewise, skimmer 13 has an aperture to accommodate suction piping 19. Portions of the piping referred to at 14, 15, 16, 17, 18, 19, and 20 are above the frost line and all water must be expunged therefrom to prevent freezing and damage to the piping system.
It is one object of the present invention to reduce the volume of water that must be drained from a pool during the winterization process.